Calc's layout makes it easy to organize information into rows and columns. As you can see in the example, we have salespeople listed alongside the left column, customers in the second column, invoice date in the third column, and revenue in the fourth column. At the moment, no formulas are entered to help you interpret the data. Clicking the E21 cell selects it and allows you to enter in a formula in the top formula bar. If you enter in the equal sign, Calc knows that what you are entering is a formula and works accordingly.

In our example, we want to know the total revenue brought in up to now, so we need to enter in the formula =sum(E4:E20) and press Return. Calc automatically enters the result into cell E21. Now we want to see what the average order value was. To do this, we have to obtain how many orders there were. For this we can use the counta function to count the number of entries in a given list. This is usually used when you need to find out how many entries there are in a text list. So, in cell B21, enter =counta(B4:B20) and press Enter. Calc now counts the number of entries in the range and returns the total in B21. All that remains for us to do is divide the total revenue by the number of orders to find the average order value. So, in cell E22, enter the formula =E21/B21 to get the average order value.